Heat storage device using fusible material

ABSTRACT

A multiroom heating-cooling system of the type wherein a water loop extends through a plurality of room air-conditioning units to exchange heat therewith, the improvement comprising a novel heat storage mechanism for absorbing heat from the water loop during daytime operations and giving back the absorbed heat to the water loop during nighttime operations, thereby reducing the amount of heat energy required to be added to the circulating water by central station equipment.

United States Patent Inventor Herbert M. Brody Carteret, NJ.

Appl. No. 52,467

Filed July 6, 1970 Patented Dec. 28, 1971 Assignee American Standard Inc.

New York, N.Y.

HEAT STORAGE DEVICE USING FUSIBLE MATERIAL 7 Claims, 7 Drawing Figs.

U.S. Cl 165/22, 165/50 Int. Cl F241 3/00 Field of Search 165/18, 22, 29, 50, 62

[56 References Cited UNITED STATES PATENTS 2,715,514 3/1955 Stair 165/50 3,165,148 1/1965 Soule 165/29 3,523,575 8/1970 Olivieri 165/22 Primary ExaminerCharles Sukalo Attorneys-John E. McRae, Tennes I. Erstad and Robert G.

Crooks ABSTRACT: A multiroom heating-cooling system of the type wherein a water loop extends through a plurality of room air- I conditioning units to exchange heat therewith, the improvement comprising a novel heat storage mechanism for absorbing heat from the water loop during daytime operations and giving back the absorbed heat to the water loop during nighttime operations, thereby reducing the amount of heat energy required to be added to the circulating water by central station equipment.

a as I IIEAT STORAGE DEVICE USING FUSIBLE MATERIAL THE DRAWINGS FIG. I is a schematic view of a room cooling-heating system incorporating the invention.

FIG. 2 is an enlarged sectional view taken through a water heater utilized in the FIG. 1 system. 7

FIGS. 3 and 4 are cross-sectional views taken on lines 3--3 and 4-4 respectively in FIG. 2.

FIG. 5 is an enlarged view of a structural detail employed in the FIG. 2 structure.

FIG. 6 is a chart depicting the performance of the FIG. 1 system when utilizing the FIG. 7 control circuit.

FIG. 7 is a simplified electrical circuit that can be used to control the FIG. 1 system.

FIG. 1 IN DETAIL The system of FIG. 1 comprises a number of room'air-conditioner' units 12, one of which is shown in some detail, and another of which is illustrated merely as a block. In practice a large number of units would be employed, as described for .example in U.S. Pat. No. 3,165,148 issued to J. Soule on Jan. 12, 1965. A representative unit comprises a self-contained reverse cycle refrigeration machine which includes a refrigerant compressor l4, air-contacted refrigerant coil 16, water-contacted refrigerant coil 18, and reversing valve 20. In its illustrated position valve allows high-pressure refrigerant gas from compressor 14 to flow through coil 16. Fan 22 passes room air over the coil to condense the refrigerant and thus heat the air. The condensed refrigerant flows across a restrictor '24 and through coil 18 where it undergoes evaporation; water flowing through an inner coil 19 supplies heat for vaporization of the refrigerant. Evaporated refrigerant is drawn through lines 26 and 28 back to the compressor. 7

Rotational adjustment of reversing valve20 allows highpressure refrigerant gas from compressor 14 to be delivered through line 26 for condensation incoil I8. Condensed refrigerant flows acrossrestrictor 24 into coil l6'where it undergoes evaporation,-thus coolingthe air supplied by fan 22.

It will be seen that in the illustrated position of the valve 20 coil I6 acts as a-refrigerant condenser to heat the room air, while coil 18 acts as a refrigerant evaporatorto absorb heat from the water flowing through coil '19. In .the nonillustratcd position of valve 20 coil .16 acts as arefrigerant evaporator to cool the air supplied by fan 22, while coil 18 acts as, a refrigerant condenser to reject heat to the water flowing through coil '19. r

The various coils .19 inthe room air-conditioning'units 12 are each continually supplied with water (or othersimilarheat exchange liquid) by meansof a central water'loop which includes one or more continuously energized water pumps 30, water heater 32, main water supply line 34, branch supply lines 36 for the individual air-conditionerunits, branch return lines 38 from the individual units, and main-return lines 40, and 44.

.Main return line 40 delivers the loop water to a heat exchange coil 50 formingpart of a coolingtower 52. Fan 53 draws air into the cooling'tower through an inlet opening 55 and thence upwardly betweenthe fins of coil '50. These fins are supplied with water sprays or other coolantfrom overhead spray nozzles 57; a suitable water pump 59 is arranged to recirculate water from a sump6l to the spray nozzlessUpward air flowby fan 53 produces evaporation of the wateronthe exterior surface of coil'50 which acts to cool the liquid flowing through the coil interior.

LOOP WATER TEMPERATURE CONTROL It is intended that waterflowing through the loop will be maintained in a temperature range between about 60 and 90 F. by selective operation of cooling tower5-2 and waterheater 32. Water in such a temperature range acts alternately as a heat source or heatsinkfor the coils 18 in the various room units 12, thereby:permitting economical operation ofsaid units as explained in U.S. Pat. application. Ser. No. 736,4l6 filed June 12, I968 in the name of J. B. Olivieri, and aforementioned U.S. Pat. No. 3,l65,l48 issued to .l. P. Soule.

During some portions of the year the various air-conditioning units 12 may be primarily on their air-cooling cycles during day periods and on their air-heating cycles during night periods. Under these circumstances operating economies can be achieved if the loop water is permitted to absorb the heat generated in each coil 18 during the day hours and to give back the heat to each coil 18 during the night hours. Aforementioned U.S. Pat. application, Ser. No. 736,416 now U.S. Pat. No. 3,523,575 granted Aug. ,1 l, 1970, proposes a large water storage tank in the loop circuit for increasing the quantity of water in the loop circuit for increasing the quantity of water in the loop circuit, thereby enabling the water to store increased quantities of heat.

The present invention seeks to achieve heat storage without a large storage tank and without increasing the quantity of water in the loop circuit. In the present invention the loop water is caused to flow through a heat exchange unit which contains a quantity of fusible material having a fusion temperature within the operating range of the loop water (preferably near 75 F. which is the midpoint of the operating range in the illustrated system). The.fusible material is able to absorb relatively large quantities of heat as it undergoes the transition from the solid to the liquid state, and to give back large quantities of heat to the loop water as it undergoes the transition from the liquid state to the solid state.

CONSTRUCTION OF WATER HEATER 32 In some instances it may be practical to incorporate the heat storage device as part of water heater 32. FIGS. 2 through 4 illustrate a water heater construction which includes the heat storage device. As there shown, the heater includes a rectangular tank 60 having a removable cover 62. Arranged within the tank are three finned heat exchange coils, each comprising a serpentine water coil 64 and transverse plate type fins 66 suitably affixed thereto, as by mechanical expansion of the coil walls .into gripping engagement with fin collars, (not shown). U.S. Pat. No. 3,437,l33 issued to R. H. Bullard on Apr. 8, 1969 describesgenerallyone process that can-be used to form the finned coil.

Eachcoil may be connected to an inlet header pipe 70 and an outlet header pipe 72; said header pipes extending transverse to-the various coils and being arranged so that header 70 receives water from pump 30 (FIG. 1) and header 72 discharges .waterto the main watersupply line 34. With such an arrangement each coil 64 handles one-third of the water flowing through the loop circuit. The number of individual coils will of course vary depending on the size of the air-conditioning system and the quantity of waterrequired to be circulatedthrough the loop.

The illustrated waterheater 32 is adapted to be heated electrically, asby individual electrical heating elements 74 of serpentine configuration. The vertical edges of the fins on each coil 64 may be equipped with a number of notches or slots 76 for. reception of the serpentine heating elements 74.

As shown in Hg. 5, each heating element may include a cylindrical metallic sheath 78 formed for example of stainless steel or inconel, ceramic electrical insulation 80 formed for example of compacted magnesia, and twospaced nichrome heater wires 82. The heater wires extend the full length of the sheath 78 butare-spaced from the sheath and from each other.

One end of sheath 78 may be closed, as at 84 (FIG. 4), and the two wires -82 electrically connected together adjacent the sheath closed end; the two wires thereby collectively form one continuous heater element extending back and forth within the sheath 78. Exposed ends 82a of the wires 82 can be connected to a suitable source of electrical power (not shown). The electrical heating elements can be standard sheathed heating elements of the type supplied by American Standard .ACI'O Research Instrument Department, 9000 King Street,

Franklin Park, Ill. under its trademark Aerorod."

If it were desired to employ a gas-fired heater or oil-fired heater for heater 32, then in that event the heat storage device might be built as a tube-shell heat exchanger separate from the heater. The heater could be a conventional hot water boiler, and the tube-shell heat exchanger could also be a conventional unit arranged with the loop water flowing through the tubes and the fusible material surrounding the tubes in the shell side; the fusible material would of course continuously remain in the heat exchanger as a stagnant heat sink.

ACTION OF FUSIBLE HEAT STORAGE MATERIAL In the illustrated'arrangement tank 60 is preferably filled with a fusible heat storage material at least to the level of the upper edges of fins 66 so that each water coil and its two electrical heating elements 74 are emersed in the fusible material. Assuming that the fusible material has a fusion temperature of 75 F., and that the temperature in the water flowing through the water loop is at some higher value, for example 80 F., the continuous stream of water through each coil 64 will cause heat to be transferred from the water to the fusible material, thereby lowering the water temperature toward 75 F. and promoting fusion of the surrounding material; heat rejected to the fusible material is thereby made available for subsequent return to the loop water should the loop water temperature drop below the fusion temperature, as for example to a value of 70 F.

Nonelectric heat transfer back and forth between the loop water and the fusible material may occur principally during the spring and fall months of the year when most of the individual room units 12 are primarily on their air-cooling cycles during the day periods. During the night most of the individual coils 18 may be absorbing heat from the loop water so that the loop water temperature will tend to fall below the illustrated 75 F. setting; as this occurs the fusible material in tank 60 will tend to solidify, thereby giving up its heat of fusion to the water and restoring the water to the 75 setting. During the day coils 18 may collectively reject heat to the loop water, thereby tending to raise the loop water temperature above the 750 F. setting; as this occurs the fusible material in tank 60 will tend to liquify, thereby extracting the equivalent heat of fusion from the loop water and lowering the water temperature to the 75 F. setting.

CHOICE OF FUSIBLE MATERIALS It is believed that various substances might be utilized for the fusible material. For example the following text book materials may be suitable:

Heat of Fusion Material Fusion Temp. C. caL/gram The optimum quantity of fusible material required for any given installation will depend on different factors, including geographical location, building size, type of occupancy, and internal lighting load, as discussed generally in aforementioned Pat. application, Ser. No. 736,416. Partial operating economics can be achieved using quantities of fusible material less than the maximum calculated for temporary heat storage during the severest operating period. However, a typical building might as an optimum require 5,000,000 B.T.U. heat storage capacity in tank 60. Assuming a material having a heat of fusion of 30 calories per gram and an average specific heat of 0.4 calories per gram, the desired storage capacity could be satisfied by approximately 16,000 pounds of fusible material. Depending on the specific gravity of the material, this might translate into about 2,000 gallons. Tank 60 would then be sized at about 30 cubic feet capacity. Such a tank would be considerably smaller than that proposed in U.S. Pat. application, Ser. No. 736,416 now Pat. No. 3,523,575 granted Aug. I I, 1970.

ILLUSTRATIVE CONTROL CIRCUIT FIG. 7 illustrates an electrical control circuit that might be employed to control the cooling tower 52 and heater 74. This circuit includes one or more thermostatic bimetals responding to the temperatures in loop water line 34. The bimetal control is arranged to close the circuit to the cooler 52 only when the line 34 temperature is above 78, and to close the circuit to the heater only when the line 34 temperature drops below 72"; at line 34 temperatures between 72 and 78 neither the heater nor the cooler can be energized. In the FIG. 7 circuitry numerals 52 and 74 are switches controlling the respective cooler and heater.

It is assumed that when the fusible material is in the molten state its heat of fusion is sufficient to keep the temperature in line 34 within the range between 72 and 78. The fusible material can go completely to a subcooled solid state only when it has insufficient heat energy to keep the line 34 temperature above 72, as at time A (FIG. 6). Conversely the fusible material can go completely to a superheated liquid state only when it is unable to keep the line 34 temperature below 78", as at timeB (FIG.6).

The'control circuit ensures that the heater or cooler can be energized only after the fusible material has given up its entire heat of fusion to the water or absorbed its entire heat of fusion from the water. With this arrangement the heater and cooler are energized only when necessary. The fusible material is allowed to serve its heat-absorbing and heat-rejecting junction without inadvertant energization of the heater and cooler.

During the hottest periods of the year the cooler 52 may be energized a large percentage of the time, and during the coolest periods of the year the heater 74 may be energized a large percentage of the time. During spring and fall periods the daytime-generated heat from coils 18 may be absorbed by the fusible material and rejected back to the loop water during the nighttime periods, thus substantially reducing the percentage of time that heater 74 or cooler 52 is required to be operated. If sufficient quantities of fusible material are used neither the heater nor the cooler need be energized during certain days of the year.

Iclaim:

1. In a room heating-cooling system comprising a plurality of room-conditioning units, at least some of which include reversible refrigeration machines which individually include an air-contacted coil, a liquid-contacted coil, a refrigerant compressor, and refrigerant control means operable to selectively cause the air-contacted coil to (I) operate as a refrigerant evaporator and the liquid-contacted coil to operate as a refrigerant condenser, or (2) cause the air-contacted coil to operate as a refrigerant condenser and the liquid-contacted coil to operate as a refrigerant evaporator: the improvement comprising a closed liquid loop circulation circuit having branches connected with each liquid-contacted coil to exchange heat with the refrigerant flowing therethrough, a central liquid cooling means for heating the loop liquid when its temperature rises abovea high-limit setting, a central liquid heating means for heating the loop liquid when its temperature falls below a predetermined low limit setting, and a heat storage device arranged to exchange heat with the loop liquid for maintaining the loop liquid temperature at a value intermediate of the highand lowtemperature settings. said heat storage device comprising a contained mass of fusible material reversibly transformable between the solid and liquid states in the temperature range between the highand low-temperature settings.

2. The system of claim 1 wherein the central liquid heating means is an electrical heating means emersed in the fusible material.

3. The system of claim 1 wherein the heat storage device comprises a tank for containment of the fusible material, and at least one liquid flow coil immersed in the fusible material.

4. The system of claim 3 wherein the liquid flow coil is a finned tube unit.

5. The system of claim 4 wherein the liquid heating means comprises sheathed electrical heating elements extending through openings in the tube fins.

6. The system of claim 1 wherein the fusible material has a solid-liquid transition temperature of approximately 75 F.

7. The system of claim 1 and further comprising a temperature responsive control device arranged to l energize the heating means when the loop liquid temperature approaches the low-limit setting, (2) energize the cooling means when the loop liquid temperature approaches the high-limit setting, and (3) lockout the heating means and cooling means while the loop liquid temperature is between the highand low-settings.

I II I t l 

1. In a room heating-cooling system comprising a plurality of room-conditioning units, at least some of which include reversible refrigeration machines which individually include an air-contacted coil, a liquid-contacted coil, a refrigerant compressor, and refrigerant control means operable to selectively cause the air-contacted coil to (1) operate as a refrigerant evaporator and the liquid-contacted coil to operate as a refrigerant condenser, or (2) cause the air-contacted coil to operate as a refrigerant condenser and the liquid-contacted coil to operate as a refrigerant evaporator: the improvement comprising a closed liquid loop circulation circuit having branches connected with each liquid-contacted coil to exchange heat with the refrigerant flowing therethrough, a central liquid cooling means for heating the loop liquid when its temperature rises above a high-limit setting, a central liquid heating means for heating the loop liquid when its temperature falls below a predetermined low limit setting, and a heat storage device arranged to exchange heat with the loop liquid for maintaining the loop liquid temperature at a value intermediate of the highand low-temperature settings, said heat storage device comprising a contained mass of fusible material reversibly transformable between the solid and liquid states in the temperature range between the high- and low-temperature settings.
 2. The system of claim 1 wherein the central liquid heating means is an electrical heating means emersed in the fusible material.
 3. The system of claim 1 wherein the heat storage device comprises a tank for containment of the fusible material, and at least one liquid flow coil immersed in the fusible material.
 4. The system of claim 3 wherein the liquid flow coil is a finned tube unit.
 5. The system of claim 4 wherein the liquid heating means comprises sheathed electrical heating elements extending through openings in the tube fins.
 6. The system of claim 1 wherein the fusible material has a solid-liquid transition temperature of approximately 75* F.
 7. The system of claim 1 and further comprising a temperature responsive control device 90 arranged to (1) energize the heating means when the loop liquid temperature approaches the low-limit setting, (2) energize the cooling means when the loop liquid temperature approaches the high-limit setting, and (3) lockout the heating means and cooling means while the loop liquid temperature is between the high- and low-settings. 